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Troubleshooting Trailer with LED Taillights that Causes Tow Vehicle to Have Dim Lights


Thanks, We have tested the 4 way wiring harness and the voltage checks out. The trailer is brand new and has been checked as well. Both work fine without each other, and with other tow vehicles and trailers. We the checked and replaced the fuses and the parking light relay on the truck. The harness is a plug and play harness just like the one you have here: Since it appears that both and truck and the trailer do not have any wiring shorts or ground issues could it be that it needs a module or converter? On the list website it says Installation Notes: Exterior mounted plug on some or all models. May require an aftermarket electrical mounting box or bracket sold separately Per Dodge owners manual: If trailer is with more than standard lighting 1 taillight per side, use of ModuLite® or dealer supplied harness is required ?? I also found information about this under a similar question: So I guess my questions are: do I need the ModuLite harness, do you sell them, and can I install it myself? Im new to wiring and electrical fixes. The company that I purchased the trailer from said that the LED lights use less power than the standard lights and they dont believe the 4 LED lights would be drawing more from the trucks light system then 2 standard lights would. But when we hook the truck and trailer together the trucks running lights dim and only 1 of the 4 LED lights on the trailer lights up and it is dim. But when we apply the brakes and the turn signals, they all work correctly and are bright on the trailer. Weve noticed this problem 3 out of the 5 times weve towed the trailer. All of these times were during the early morning or after a rain event. So our other thought was that possibly humidity or condensation was playing a role. Because the 2 times it worked fine there was less humidity and no previous rain. We are working our way through the troubleshooting page I will double check the ground on the truck. The trucks wiring harness does not have a power converter. Thanks for your help.


Expert Reply:

That is a pretty bizarre issue you are having, but I believe the solution would be to go with a modulite style trailer wiring harness like the # 119190KIT as it sounds like the LED lights of your trailer are causing the lights of your vehicle to be very dim. Without getting overly technical, the LEDs draw considerably less power than an incandescent. It sounds like the LEDs of your trailer are causing the running lights of your taillights to only draw the same amount of amperage as them so the lights end up much dimmer.

expert reply by:
Jameson C

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